Download The Periodic Table

The Periodic Table
Unit 3/Chapters 3 & 8 Notes
Chemistry CPA
Periodic Trends
• Many properties of atoms depend on the strength
of attraction between the outer shell electrons and
the nucleus
• This attraction will depend on:
1. The positive charge that attracts the other shell
electrons
2. The distance of electrons from the nucleus
Four Periodic Trends
1.
2.
3.
4.
Atomic Radius
Ionization Energy
Electronegativity
Electron Affinity
Atomic Radius
What is it?
• Diameter of atom
What happens down a group?
• Increases
• since there is an increase in the number of shells.
What happens across a period?
• Decreases
• since there is an increase in core charge, the outer shell electrons are
attracted closer to the nucleus (it’s the same shell but there are more
electrons in the shell as you move across the period)
Atomic Radius decreases across a period
Atomic Radius increases down a family/group
Ionization Energy
ee
ee
e
e
• What is it?
• Amount of energy required to
remove the highest energy electron
from an atom. (or steal one electron)
• What happens down a group?
• Decreases; since the size of the atom is increasing, the attraction is weaker
between the outer shell electrons and the nucleus. Therefore electrons are
easier to remove.
• What happens across a period?
• Increases; since there is an increase in core charge, the attraction is greater
between the outer shell electrons and the nucleus. Therefore electrons are
harder to remove.
Ionization Energy
• In other words…
• If its easy to steal a electron, it has low ionization
energy
• If its hard to steal an electron, it has a high
ionization energy
• The smaller the atom, the harder to steal an
electron
• The larger the atom the easier it is to steal an
electron
Ionization Energy
Electronegativity
• What is it?
• Measure of the ability of an atom to attract an electron towards itself
or love of electrons!
• What happens down a group?
• Decreases; since the electrons are further from the nucleus, there is a
weaker attraction
• What happens across a period?
• Increases; since there is an increase in core charge, there is a greater
attraction of the outer shell electrons to the nucleus.
Electronegativity
Electron Affinity
• What is it?
• The energy release when an electron is added to an atom. Most favorable
toward NE corner of PT since these atoms have a great affinity (“love and
happiness”) for e-. (Think of “Jumping for Joy”!)
• What happens down a group?
• Decreases; since the electrons are further from the nucleus, the atom has
no desire to hang on to it’s electron, so it won’t release too much
“Happiness” (energy) if it gains one.
• What happens across a period?
• Increases; the more electrons an atom has in it’s valence shell, the more
“happy” it will become when it gets closer to completing it shell.
Electron Affinity